Dopamine Signals the Value of Delayed Rewards

Dopamine
is the chemical messenger in the brain most closely associated with pleasure and
reward. Recent scientific advances now shed light on precise roles for dopamine
in the reward process.

A
new paper published in the current issue of Biological
Psychiatry implicates dopamine in a person’s ability to be motivated by
delayed rewards.

People
like immediate reinforcement and tend to devalue rewards that are substantially
delayed in time. As a result, people will often opt for smaller immediate
rewards as opposed to larger delayed rewards when given a choice.

This
decision-making process of weighing benefits versus costs for a particular
outcome is called “delay discounting”. Though we perform these cost-benefit
analyses in a seemingly effortless manner, scientists are still learning how
the brain performs these complex processes.

In
the current study, researchers at the University of North Carolina at Chapel
Hill and Stanford University used rodent models to examine the role of this
neurotransmitter in dynamically tracking specific elements of value-based
decision making.

First,
they trained one set of rats to choose between two different options, a small
sweet reward that could be eaten right away, or a bigger sweet reward that was
delivered only after varying delays.

Senior
author Dr. Regina Carelli explained their findings, “We found that dopamine
signaled the more preferred option; more dopamine was observed for cues
signaling immediate large rewards, but this declined as the delay to the large
reward increased.” This shift in in dopamine release and associated tendency to
choose smaller immediate rewards over larger delayed rewards is consistent with
the phenomenon of delay discounting.

Next,
using a technique known as optogenetics in a second set of rats, they precisely
controlled the activity of dopamine neurons during cues that signaled large or
delayed rewards. This experiment revealed that, by ‘playing back’ the patterns
of dopamine release observed in the first set of rats (when they were pondering
which choice to make), the researchers could bias them toward making different
decisions in the future.

“These
exciting new findings suggest that dopamine plays a sophisticated role in
helping to guide specific aspects of decision-making behavior,” Carelli added.

Dr.
John Krystal, Editor of Biological
Psychiatry, commented, “Delay discounting is an important and poorly
understood process. Understanding how it works sheds light on how dopamine
signals reward in the brain. It also may help to develop preventive strategies
for drug abuse, gambling disorders, and other clinical conditions where delay
discounting may play a role.”

Notes for editorsFull text of the article is available to credentialed journalists
upon request; contact Rhiannon Bugno at +1 214 648 0880 or Biol.Psych@utsouthwestern.edu. Journalists
wishing to interview the authors may contact Dr. Regina Carelli at +1 919 962
8775 or rcarelli@unc.edu.

The
authors’ affiliations, and disclosures of financial and conflicts of interests
are available in the article.

John
H. Krystal, M.D., is Chairman of the Department of Psychiatry at the Yale
University School of Medicine, Chief of Psychiatry at Yale-New Haven Hospital,
and a research psychiatrist at the VA Connecticut Healthcare System. His
disclosures of financial and conflicts of interests are available here.

About
Biological PsychiatryBiological Psychiatry is the official journal of the Society of Biological Psychiatry, whose purpose is to promote
excellence in scientific research and education in fields that investigate the
nature, causes, mechanisms and treatments of disorders of thought, emotion, or
behavior. In accord with this mission, this peer-reviewed, rapid-publication,
international journal publishes both basic and clinical contributions from all
disciplines and research areas relevant to the pathophysiology and treatment of
major psychiatric disorders.

The journal publishes novel results of original research
which represent an important new lead or significant impact on the field,
particularly those addressing genetic and environmental risk factors, neural
circuitry and neurochemistry, and important new therapeutic approaches. Reviews
and commentaries that focus on topics of current research and interest are also
encouraged.

Biological Psychiatry is one of the most selective and highly cited journals in
the field of psychiatric neuroscience.
It is ranked 5th out of 135 Psychiatry titles and 14th
out of 251 Neurosciences titles in the Journal Citations Reports® published by
Thomson Reuters. The 2013 Impact Factor score for Biological Psychiatry
is 9.472.

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